WO2004017411A1

WO2004017411A1 - Solid-state imaging device and its manufacturing method

Info

Publication number: WO2004017411A1
Application number: PCT/JP2003/010217
Authority: WO
Inventors: Kazushi Wada; Koichi Harada; Shuji Otsuka; Mitsuru Sato
Original assignee: Sony Corporation
Priority date: 2002-08-12
Filing date: 2003-08-11
Publication date: 2004-02-26
Also published as: US8217431B2; US7535038B2; TWI266418B; CN100474607C; JP4613821B2; JPWO2004017411A1; TW200409351A; KR20050048600A; US20090194794A1; CN1685516A; KR101016539B1; US20060163617A1

Abstract

The crosstalk between adjacent pixels is prevented by a structure in which an overflow barrier is provided in a deep portion of a substrate. A local P-type region (150) is formed in a predetermined position in a lower layer region below a vertical transfer register (124) and a channel stop region (126). The potential in the lower layer region below the vertical transfer register (124) and the channel stop region (126) is controlled by the P-type region (150) so that the potential in the extent from the minimum potential position of the vertical transfer register (124) to the overflow barrier (128) in the lower layer region is lower than that in the lower layer region below a photosensor (122). Therefore, because the potential in the lower layer region below the vertical transfer register (124) and the channel-stop region (126) on both sides is low, the charge produced by the photoelectric transducing in the sensor region is blocked by this potential barrier and cannot diffuse easily. Thus, the crosstalk between adjacent pixels can be prevented.

Description

Specification

Technical Field

The present invention relates to a solid-state imaging device provided with a plurality of pixels using a photoelectric conversion unit on a semiconductor substrate and a CCD transfer unit for transferring signal charges generated by the pixels, and particularly to an excess charge generated by the photoelectric conversion unit. The present invention relates to a solid-state imaging device having a vertical overflow barrier structure for discharging sapphire toward the back surface of a semiconductor substrate. Background art

Conventionally, a CCD image sensor having pixels arranged in a matrix has been known as this type of solid-state imaging device.

FIG. 10 is a plan view showing a general configuration example of a conventional CCD image sensor.

In this CCD image sensor, a photosensor (photodiode) 22 serving as a photoelectric conversion unit that serves as a pixel is provided in an imaging area 20 provided on a semiconductor substrate (Si substrate, semiconductor chip) 10. A plurality of vertical transfer registers 24 and a channel stop area 26 are arranged for each photo sensor row, and a horizontal transfer register 32 and an output section are arranged outside the imaging area 20. 3 4 is provided.

The outside of the imaging area 20 is a peripheral area 21 where bus lines and the like are arranged.

The signal charge generated by each photo sensor 22 is read out to the vertical transfer register 24, transferred in the vertical direction for each photo sensor column, and sequentially output to the horizontal transfer register 32.

The horizontal transfer register 32 transfers the signal charge of each photosensor 22 transferred by the vertical transfer register 24 in the horizontal direction for each row. And outputs them sequentially to the output unit 34.

The output unit 34 sequentially converts the signal charges transferred by the horizontal transfer register 32 into a voltage signal, applies a voltage to the signal, and outputs the signal.

In addition, the channel stop region 26 prevents signal leakage between adjacent photosensor rows.

FIG. 11 is a cross-sectional view showing the internal element structure of the CCD image sensor shown in FIG.

As shown in the figure, a photo sensor 22, a vertical transfer register 24, and a channel stop region 26 are formed on a semiconductor substrate (Si substrate) 10. On the upper surface, a transfer electrode (polysilicon film) 44 of the vertical transfer register 24 is disposed via an insulating film (silicon oxide film) 42, and a light shielding film 46 is mounted thereon. .

An opening 46A is formed in the light-shielding film 46 so as to correspond to the light receiving area of the photosensor 22, and light enters the photosensor 22 through the opening 46A.

The photosensor 22 has an upper P + layer 22 A and a lower N layer 22 B, and holes generated by photoelectric conversion are taken into the P + layer 22 A, and the N layer 2 2 B generates a signal charge.

The signal charges generated in the N layer 22B are accumulated in a depletion layer formed below the N layer 22B, and are read out between the photosensor 22 and the vertical transfer register 24. The data is read from the photo sensor 22 to the vertical transfer register 24 by the operation of the gate section.

Also, in the internal region of the semiconductor substrate 10, an overflow flow barrier (OFB) 28 for storing the signal charge generated by each photosensor 22 in the lower region of the N layer 22B is provided. Is provided.

The overflow barrier 28 adjusts the impurity distribution in the semiconductor substrate to form a potential in the internal region of the semiconductor substrate 10. It forms a barrier by the signal and prevents leakage of signal charges. Also, when an excessive amount of light is incident, the signal charge excessively generated by the photo sensor 22 is discharged to the back side of the semiconductor substrate 10 over the overflow barrier 28.

In such a CCD solid-state imaging device as described above, the development of technology for improving the sensitivity per unit area is urgently required as the size of the unit pixel is reduced.

As one of the measures, the overflow barrier, which is conventionally formed about 3 μm from the surface of the Si substrate, is formed at a deeper position (for example, 5 tm to 10 m). You could think so.

If the potential of the conventional vertical transfer register is formed in this state, the distribution is as shown in FIG. 12 and FIG.

That is, FIG. 12 is an explanatory diagram showing the distribution of the potential in each substrate cross section of the photosensor and the vertical transfer register. The vertical axis represents the depth of the potential, and the horizontal axis represents the depth from the substrate surface. I have. The solid line A shows the potential distribution in the photosensor portion, and the broken line B shows the potential distribution in the vertical transfer register portion.

Fig. 13 is an explanatory diagram showing the distribution of potential in the photosensor region in a three-dimensional manner. The X-axis shows the horizontal direction, the Y-axis shows the potential depth direction, and the Z-axis shows the substrate depth direction. The plane constituted by the X axis and the Y axis indicates the substrate surface.

In FIGS. 12 and 13, the vertical axis in FIG. 12 and the Y axis in FIG. 13 indicate that the potential is higher from the top to the bottom. Also, the numerical values of the scales attached to each axis are values adjusted for convenience.

In such a potential distribution, in a deep part of the substrate, the position of the potential of the photosensor is equal to the position of the potential of the lower part of the vertical transfer register. Therefore, in such a state, the charge photoelectrically converted in the sensor area diffuses in the horizontal direction (indicated by an arrow D in FIG. 13), and enters the sensor area of an adjacent pixel, a problem called crosstalk. There is a problem that occurs.

Therefore, an object of the present invention is to provide a solid-state imaging device capable of effectively preventing crosstalk between adjacent pixels even when an overflow barrier is provided deep in a substrate. Disclosure of the invention

In order to achieve the above object, the present invention provides a plurality of pixels including a photoelectric conversion unit that is provided on a semiconductor substrate and generates a charge according to the amount of incident light, and is formed on the semiconductor substrate and read from the pixel. A transfer unit configured to transfer the charge; and an overflow barrier formed inside the semiconductor substrate and configured to discharge a surplus charge generated in the pixel toward a back surface of the semiconductor substrate. The potential of the lower region of the transfer section is formed to be smaller than the potential of the lower region of the photoelectric conversion section between the minimum potential position of the transfer section and the overflow barrier. It is characterized by. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing a device structure of a CCD image sensor according to a first embodiment of the present invention. FIG. 2 is a sectional view showing a photo sensor and a vertical transfer register of the CCD image sensor shown in FIG. FIG. 3 is an explanatory diagram showing a potential distribution on a cross section of a substrate. FIG. 3 is an explanatory diagram showing a three-dimensional distribution of a potential in a photosensor region of the CCD image sensor shown in FIG. 1, and FIG. 2 shows the element structure of a CCD image sensor according to a second embodiment. FIG. 5 is an explanatory diagram showing a potential distribution in a cross section of each substrate of the photo sensor, the vertical transfer register, and the pixel-to-pixel portion of the CCD image sensor shown in FIG. 4, and FIG. Shown in Figure 4

FIG. 7 is an explanatory view three-dimensionally showing a potential distribution in a photosensor region of the CCD image sensor. FIG. 7 is a cross-sectional view showing a method of forming an overflow barrier of the CCD image sensor shown in FIG. 4, and FIG. FIG. 9 is a cross-sectional view showing the element structure of a CCD image sensor according to a third embodiment of the present invention. FIG. 9 shows a photo sensor, a vertical transfer register, and an inter-pixel portion of the CCD image sensor shown in FIG. FIG. 10 is an explanatory diagram showing a potential distribution in each substrate cross section. FIG. 10 is a plan view showing a device arrangement of a conventional CCD image sensor. FIG. 11 is a device structure of the CCD image sensor shown in FIG. FIG. 12 is a cross-sectional view showing the potential distribution of the photo sensor and the vertical transfer register of the CCD image sensor shown in FIG. A bright view, FIG. 1 3 is an explanatory diagram sterically showing a distribution of Po Tensharu in follower Tosensa region of C C D image sensor shown in FIG. 1 0. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the solid-state imaging device according to the present invention will be described.

FIG. 1 is a cross-sectional view showing an internal element structure of a CCD image sensor according to a first embodiment of the present invention. Note that the element arrangement in the planar direction of the CCD image sensor in this example is common to that of the conventional example shown in FIG. 10, and FIG. 1 shows a cross section taken along line aa of FIG.

As shown in FIG. 1, the image sensor of this example has a photo sensor 122 and a vertical transfer register on the upper layer of a semiconductor substrate (Si substrate) 110, similarly to the image sensor shown in FIG. 1 2 4, and channel stop area A region 126 is formed, and a transfer electrode (polysilicon film) of a vertical transfer register 124 is placed on an upper surface of the semiconductor substrate 110 via an insulating film (silicon oxide film) 142. 4 is arranged, and a light shielding film 1 4 6 is mounted thereon.

The light-shielding film 146 has an opening 146A corresponding to the light receiving area of the photosensor 122, and light enters the photosensor 122 through the opening 146A. .

The photosensor 122 has an upper P + layer 122 A and a lower N layer 122 B, and holes generated by photoelectric conversion are taken into the P + layer 122 A, Signal charges are generated in the N layer 122B.

The signal charges generated in the N-layer 122B are accumulated in a depletion layer formed below the N-layer 122B, and the signal charges are generated between the photosensor 122 and the vertical transfer register 124. The data is read from the photosensor 122 to the vertical transfer register 124 by the operation of the read gate unit provided in the memory.

In this example, a configuration is shown in which one N layer 122 B is provided below the P + layer 122 A, but the overflow layer and the depletion layer are located deep in the substrate 110. In the case of forming a layer, a low-concentration N− layer may be provided below the N layer 122 B.

In addition, an overflow barrier (OFB) 128 for storing signal charges generated by the photosensors 122 in the lower region of the N layer 122B is provided inside the semiconductor substrate 110. Is provided.

The overflow barrier 128 forms a barrier due to a potential in the internal region of the semiconductor substrate 110 by adjusting the impurity distribution in the semiconductor substrate, and prevents leakage of signal charges. is there. Also, when an excessive amount of light is incident, the signal charges excessively generated by the photo sensor 122 are discharged to the back side of the semiconductor substrate 110 through the overflow barrier 128. . In the semiconductor substrate 110, a high-resistance layer 110B is provided on the N-type substrate 11OA by a predetermined method (for example, epitaxial growth), and various elements are formed on the high-resistance layer 11OB. In this case, an overflow barrier 128 is formed near the boundary between the N-type substrate 11 OA and the high-resistance layer 11 OB.

The overflow barrier 128 is formed, for example, at a depth of 5 μπι to 10 μπα from the surface of the substrate 110. <In this example, the vertical transfer register 1 A partial rectangular region 150 is formed at a predetermined position in the lower layer region of the channel top region 124 and the channel stop region 126. The rectangular region 150 forms the vertical transfer register 124 and the channel. The potential in the lower area of the stop area 1 2 6 is adjusted, and the potential in the lower area of the photo sensor 1 2 Smaller (ie, lower).

FIG. 2 is an explanatory diagram showing the potential distribution in the cross section of each substrate of the photosensors 122 and the vertical transfer registers 124.The vertical axis represents the depth of the potential, and the horizontal axis represents the depth from the substrate surface. ing. The solid line Α indicates the potential distribution in the photosensor portion, and the dashed line B indicates the potential distribution in the vertical transfer register portion. The unit of each axis can be set arbitrarily.

FIG. 3 is an explanatory view three-dimensionally showing the distribution of potential in the photosensor region, in which the X axis indicates the horizontal direction, the Y axis indicates the potential depth direction, and the Z axis indicates the substrate depth direction. The plane constituted by the X axis and the Y axis indicates the substrate surface. The unit of each axis can be set arbitrarily. The “substrate depth direction” is a direction from the front surface to the rear surface of the substrate.

2 and 3, the vertical axis of FIG. 2 and the vertical axis of FIG. The Y-axis means that the potential increases from top to bottom.

According to the potential distribution of the conventional example shown in FIGS. 12 and 13 described above, the position of the potential of the photosensor is equal to the position of the potential of the lower layer of the vertical transfer register in the deep part of the substrate. In this example, as shown in FIGS. 2 and 3, the potential in the lower layer area of the vertical transfer register 124 and the channel stop area 126 is the minimum potential of the vertical transfer register 124. Between the position and the overflow par 128, the potential of the lower part of the photosensor 122 is smaller (ie, lower) than the potential of the lower region.

Therefore, in the state of this example, the charge photoelectrically converted in the sensor area has a low potential in the lower layer area of the vertical transfer registers 124 and the channel stop area 126 on both sides, and is blocked by this potential barrier. As a result, the state cannot be easily diffused and it is difficult to leak into the sensor area of the adjacent pixel, so that crosstalk can be effectively prevented.

Next, an example of a manufacturing method for obtaining such a potential distribution according to the first embodiment will be briefly described.

First, a high-resistance substrate (high-resistance substrate of 100 Ω or more, for example, by epitaxy) is formed over the semiconductor substrate 110 (Ν substrate 11OA) (ie, from the substrate surface to the overflow barrier). The layer 110B) is formed.

In addition, a P-type impurity such as boron is ion-implanted from the surface of the semiconductor substrate 110 to form a P-type region which becomes the overflow barrier 128.

Also, the vertical transfer register 124 and the channel stop area 126 are located deeper in the lower part (above the overflow end 128). A P-type region 150 is formed by ion-implanting a P-type impurity into the layer.

In this way, a partial high-concentration P-type region 150 can be formed in the high-resistance layer 110B. However, this is only an example, and various methods can be used.

Next, a second embodiment of the present invention will be described.

In the second embodiment of the present invention, in order to exhibit a more effective barrier effect, a photo sensor unit (a photoelectric conversion unit) out of the P-type well region for forming the overflow barrier described above. By forming a partial low-concentration region in the region corresponding to (1), the potential at the overflow barrier of the vertical transfer register (transfer section) and the potential at the overflow barrier at the intermediate portion between adjacent pixels are obtained. In this case, the potential is smaller than the potential of the overflow barrier in the photosensor section, and the leakage of the electric charge in the overflow barrier is further completely prevented.

FIG. 4 is a cross-sectional view showing the internal element structure of the CCD image sensor according to the second embodiment of the present invention. Note that the same components as those shown in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted. In addition, the element arrangement in the planar direction of the CCD image sensor in this example is common to the conventional example shown in FIG. 10, and FIG. 4 shows an a-a cross section of FIG.

In the image sensor of this example, too, an overflow barrier 160 is formed near the boundary between the N-type substrate 11 OA constituting the semiconductor substrate (Si substrate) 110 and the high-resistance layer 110 B. However, in the P-type region forming this overflow flow barrier 160, a partial low-concentration region 162 is formed in a region corresponding to the photosensor 122, and other regions are formed. The area is a normal density area 164.

As a result, the overflow barrier of the vertical transfer register 124 is obtained. And the potential at the overflow barrier in the middle of the adjacent pixels is smaller (ie, lower) than the potential at the overflow barrier of the photosensor 122.

FIG. 5 is an explanatory diagram showing the distribution of the potential in the photosensors 122, the vertical transfer registers 124, and the cross-sections of the respective substrates in the middle part of the adjacent pixels. It shows the depth from the substrate surface. The solid line A indicates the potential distribution in the photosensor portion, the broken line B indicates the potential distribution in the vertical transfer register portion, and the dashed-dotted line C indicates the potential distribution in the intermediate portion between adjacent pixels. The unit of each axis can be set arbitrarily.

FIG. 6 is an explanatory view three-dimensionally showing a potential distribution in the photosensor region, in which the X-axis indicates the horizontal direction, the Y-axis indicates the potential depth direction, and the Z-axis indicates the substrate depth direction. The plane constituted by the X axis and the Y axis indicates the substrate surface. The unit of each axis can be set arbitrarily.

In FIGS. 5 and 6, the vertical axis in FIG. 5 and the Y axis in FIG. 6 indicate that the potential increases from top to bottom.

In the potential distribution of the first embodiment shown in FIGS. 2 and 3 described above, the potential of the photo sensor unit and the potential of the vertical transfer register coincide at the depth position of the overflow transistor. Then, as shown in FIG. 5 and FIG. 6, the potential at the overflow barrier 160 of the vertical transfer register 124 and the potential at the overflow barrier 160 in the middle part of the adjacent pixel are determined by the photo sensor. The potential at the overflow barrier 160 is smaller than the potential at the overflow barrier 160 (shown by the potential difference G in FIGS. 5 and 6). This further completely prevents the leakage of the electric charge, thereby obtaining the effect of suppressing crosstalk and the effect of improving sensitivity.

The difference in the impurity concentration of the overflow barrier 160 allows the overflow barrier 1 to be provided without providing the partial P-type region 150 described in the first embodiment. The potential in the lower region of the vertical transfer register 124 and the channel stop region 126 is adjusted by the impurity concentration of 60, and between the maximum potential position of the vertical transfer register 124 and the overflow barrier 128. And is formed smaller (ie, lower) than the potential in the lower region of the photosensor 122. Conversely, it can be implemented in combination with the first embodiment. The other points are the same as those of the first embodiment, and the description is omitted.

Next, two examples of a manufacturing method for obtaining a potential distribution according to the second embodiment will be briefly described.

In order to obtain the concentration distribution of the overflow barrier 160 as described above, ion implantation of a normal concentration P-type impurity into the entire overflow barrier and ion implantation of an N-type impurity into the corresponding region of the photosensor 122 are required. (First method), ion implantation of low-concentration P-type impurities into the entire overflow barrier, and ion implantation of low-concentration P-type impurities into the corresponding region of the photosensor 122. (The second method) can be used.

First, the first method will be described with reference to FIG.

In this method, P-type impurity ions are implanted into the entire area where the overflow barrier 160 is to be formed at a concentration similar to that of the related art. Next, by ion-implanting N-type impurities into the corresponding region of the photosensor 122, the P-type impurity concentration in this portion is reduced, and a low-concentration region 162 is formed. The other areas are the normal density areas 164. Next, the second method will be described with reference to FIG.

First, in FIG. 7 (A), P-type impurities are ion-implanted at a low concentration into the entire region forming the overflow barrier 160. An impurity region 16OA is formed.

Next, in FIG. 7 (B), the second ion implantation of the low-concentration P-type impurity into the vertical transfer register 124 and the corresponding area of the pixel except for the area corresponding to the photosensor 122 is performed. By doing so, the P-type impurity concentration in this portion becomes the normal concentration, and becomes the normal concentration region 164.

Further, the corresponding region of the photosensor 122 where the second ion implantation was not performed remains at a low concentration, and this becomes the low concentration region 16 2.

The dose ratio between the first ion implantation and the second ion implantation is determined by how deep the potential of the overflow barrier in the photosensor section is.

In the second method, since the same P-type impurity is implanted, it is possible to perform ion implantation without considering the range difference (boron> phosphorus> arsenic) due to the impurity. There is an advantage that the overflow barrier can be easily formed to a deeper position. Next, a third embodiment of the present invention will be described.

In the third embodiment of the present invention, the vertical transfer register (transfer section) exhibits an effective barrier effect for suppressing crosstalk and increases the potential of the photosensor section (photoelectric conversion section). By doing so, the potential difference between the photosensor section and the vertical transfer register is increased to enhance the par- ial effect.

FIG. 8 is a sectional view showing the internal element structure of a CCD image sensor according to the third embodiment of the present invention. The one shown in Fig. 1 The same reference numerals are given to the same components as those described above, and description thereof will be omitted. The element arrangement in the planar direction of the CCD image sensor in this example is common to that of the conventional example shown in FIG. 10, and FIG. 8 shows an a-a cross section of FIG.

In this example, as shown in FIG. 8, a partial P-type region 150 is independently provided at a predetermined position in the lower region of the vertical transfer register 124 and the channel drop region 126. The P-type region 150 adjusts the potential in the lower region of the vertical transfer register 124 and the channel stop region 126, and the maximum potential position of the vertical transfer register 124 is formed. It is formed smaller (lower) than the potential in the lower region of the photosensor 122 between the overflow barrier 128 and the overflow barrier 128.

Further, in this example, seven layers of partial N-type regions 151 are independently formed at predetermined positions in the lower region of the photosensor 122, and the N-type regions 15 By 1, the potential in the lower region of the photosensor 122 is adjusted, and the potential in the lower region of the photosensor 122 is formed to be larger (higher) than in the first embodiment. N-type region 151 is formed so as to have a different depth from P-type region 150.

FIG. 9 is an explanatory diagram showing the distribution of the potential in the photosensors 122, the vertical transfer registers 124, and the cross-section of each substrate in the middle part of the adjacent pixel. The vertical axis represents the potential depth, and the horizontal axis represents the potential. It shows the depth from the substrate surface. The solid line A shows the potential distribution in the photo sensor portion, and the broken line B shows the potential distribution in the vertical transfer register portion. The unit of each axis can be set arbitrarily.

In this example, as shown in FIG. 9, the potential in the lower region of the vertical transfer register 124 and the channel stop region 126 is Between the minimum potential position of the vertical transfer register 124 and the overflow barrier 128, it is formed smaller (ie, lower) than the potential of the lower region of the photosensor 122.

Further, in this example, the potential of the lower layer region of the photosensor 122 is formed larger than in the case of the first embodiment shown in FIG.

Therefore, in the state of the present example, the charge photoelectrically converted in the sensor area has a low potential in the lower layer area of the vertical transfer registers 124 on both sides and the channel stop area 126, so that this potential barrier As a result, the light cannot be easily diffused into the sensor area of the adjacent pixels, so that it is difficult to leak into the sensor area of the adjacent pixel. Thus, crosstalk can be effectively prevented. In particular, in this example, since the potential in the lower layer region of the photosensor 122 is large, the step with the potential barrier is large, and the barrier effect is stronger. Therefore, crosstalk can be more effectively prevented.

Although the P-type region 150 is formed in four layers and the N-type region 1501 is formed in seven layers in the third embodiment, the P-type region 150 is limited to four layers. However, similar effects can be obtained by forming one or more layers of P-type regions. Similarly, the N-type region 151 is not limited to seven layers, and the same effect can be obtained by forming one or more N-type regions.

In the above example, the present invention has been described with reference to a CCD image sensor in which photo sensors are arranged vertically and horizontally. However, the present invention is not limited to this, but may be applied to other solid-state imaging devices using CCDs. They can be applied in the same way.

In the above example, the case where electrons generated by the photoelectric conversion unit are handled has been described. However, the present invention may be similarly applied to a configuration using holes. this In this case, the polarity of the P and N polarities of each semiconductor region is reversed. That is, the magnitude (high or low) of the potential in the present invention has a meaning based on the absolute value.

As described above, according to the solid-state imaging device and the method for manufacturing the same of the present invention, the potential of the lower layer region of the transfer unit is set between the minimum potential position and the overflow barrier, and the lower layer of the photoelectric conversion unit is reduced. Since the potential is smaller than the potential of the region, even when the overflow barrier is formed at a deep position in the substrate, it is possible to prevent signal charges accumulated in the lower region of the photoelectric conversion portion from leaking to the adjacent transfer portion. .

Further, according to the solid-state imaging device and the method for manufacturing the same of the present invention, the potential in the overflow barrier of the transfer unit and the potential in the overflow barrier of the middle part of the adjacent pixels are reduced in the overflow barrier of the photoelectric conversion unit. Since the potential is smaller than the potential, even if the overflow barrier is formed at a deep position in the substrate, the signal charges accumulated in the lower layer region of the photoelectric conversion portion do not leak to the adjacent transfer portion or pixel side. Can be prevented.

As a result, it is possible to eliminate the occurrence of crosstalk due to the formation of the overflow barrier at a deep position in the semiconductor substrate, to prevent the image quality from deteriorating, and to increase the accumulated charge amount in each pixel. This has the effect of improving sensitivity.

Claims

The scope of the claims

1. A photo sensor unit provided on the surface of the substrate for converting incident light into electric charges;

A transfer unit formed on the surface of the substrate and transferring the charge read from the photosensor unit;

An overflow barrier formed inside the substrate, for discharging an unnecessary portion of the electric charge, wherein a potential under the transfer portion in a depth direction of the substrate is changed from the minimum potential position to the overflow barrier. A solid-state imaging device formed to be smaller than the potential below the photosensor portion over a period up to a point.

2. The solid-state imaging device according to claim 1, wherein one or more impurity regions are formed below the transfer unit.

3. The solid-state imaging device according to claim 1, wherein one or more impurity regions are formed below the photosensor portion.

4. The solid according to claim 2, wherein one or a plurality of second impurity regions formed below the photosensor portion are formed so as to have different depths from the impurity regions. Imaging device.

5. The method according to claim 4, wherein the impurity region is formed in four layers in the depth direction of the substrate, and the second impurity region is formed in seven layers in the depth direction of the substrate. Solid-state imaging device.

6. The solid-state imaging device according to claim 4, wherein the impurity region is P-type, and the second impurity region is N-type.

7. The solid-state imaging device according to claim 1, wherein a potential at the overflow barrier below the transfer unit is smaller than a potential at the overflow barrier below the photosensor unit.

8. The area under the photosensor portion of the overflow barrier has a lower concentration than that of the area in the overflow barrier. Item 9. The solid-state image sensor according to item 7, wherein

9. The solid-state imaging device according to claim 1, wherein the overflow barrier is formed at a depth of at least 3 μm from the surface of the substrate.

10. The substrate includes a first substrate of a first conductivity type, and a second substrate of a first conductivity type or a second conductivity type formed on an upper layer of the first substrate and having higher resistance than the first substrate. 2. The solid-state imaging device according to claim 1, formed from a substrate.

11. The solid-state imaging device according to claim 10, wherein the first conductivity type is N-type, and the second conductivity type is P-type.

1 2. A photosensor section provided on the surface of the substrate for converting incident light into electric charges;

An overflow barrier formed inside the substrate, for discharging an unnecessary portion of the electric charge, wherein the potential at the overflow barrier below the transfer unit is reduced by the overflow barrier below the photosensor unit. Solid-state imaging device smaller than the potential.

13. A low-density region having a lower concentration than the region other than the overflow barrier in the area below the photosensor portion of the overflow barrier. Solid state imaging device.

14. A photosensor unit provided on the surface of the substrate and converting incident light into electric charge; a transfer unit formed on the surface of the substrate and transferring the electric charge read from the photosensor unit; A method of manufacturing a solid-state imaging device, comprising: an overflow barrier formed inside a substrate, for discharging an unnecessary portion of the charge, A method for manufacturing a solid-state imaging device, comprising a step of forming one or more impurity regions in a lower layer of the transfer section on the substrate.

15. The method for manufacturing a solid-state imaging device according to claim 14, comprising a step of forming one or a plurality of second impurity regions in a lower layer of the photosensor portion.

16. The method for manufacturing a solid-state imaging device according to claim 15, further comprising a step of forming the second impurity regions so as to have different depths from the impurity regions.

17. The solid according to claim 14, further comprising a step of forming a region under the photosensor portion of the overflow barrier at a lower concentration than a region other than the region in the overflow barrier. Manufacturing method of imaging device.